There is a great interest in accurately determining the gender of an unborn child as early as possible. Available techniques are typically performed at late stages of a pregnancy. Ultrasound can be used to determine fetal gender after the 18th week of pregnancy. Polymerase chain reaction (PCR) amplification of Y-specific DNA sequences requires a sample of maternal blood, as well as expensive equipment. PCR can be carried out as early as the 6th week of gestation with an accuracy of only around 80%. Lagona et al. Multiple testing in fetal gender determination from maternal blood by polymerase chain reaction. Hum. Genet. 102, 6:1 (1998). Amniocentesis is performed after the 18th week of pregnancy; however, it carries a risk of miscarriage due to its invasiveness. Chorionic Villi Sampling (CVS), conducted between the 10th and 13th week of pregnancy, can also provide accurate information, but again, the procedure is invasive and requires costly equipment.
Alternatively, it is possible to determine the gender of an unborn child by assaying sex hormones. Sex hormones are steroids that play important roles in both normal growth and development. In addition, sex hormones influence the development of sex organs and maintenance of secondary sex characteristics in mammals. Testosterone, the principal male sex hormone, is primarily secreted by the testes of males and, to a much less extent, the ovaries of females. On average, an adult man produces about forty to sixty times more testosterone than an adult woman. Similarly, estrogen functions as the primary female sex hormone and is usually present at significantly higher levels in women than men. The urine from a mother carrying a male fetus is richer in testosterone when compared with the urine from a mother carrying a female fetus. This difference is probably due to the contribution of sex hormones secreted by fetal testes. Jost A. A new Look at the Mechanisms Controlling Sex Differentiation in Mammals. John Hopkins Med. J. 130: 38 (1972). Approaches based on a pregnant woman's individual sex hormone levels have been explored to determine fetal gender; however, thus far, they have not resulted in the development of any statistically reliable methods. For example, in one study, antibodies against testosterone were used in a radio-immunoassay to determine the testosterone levels in pregnant mothers' urine. The accuracy of this study with respect to determining fetal gender was low. Loewit et al. Determination of fetal sex from maternal testosterone excretion in early pregnancy. Dtsch. Med. Wschr. 99: 1656 (1974).
Urine from pregnant women has been used in various attempts to develop simple and non-invasive tests to determine fetal gender. Most of these procedures exploit simple characteristics of maternal urine such as its pH or the ability to form complexes with aluminum compounds. Consequently, these tests are usually associated with comparatively poor reliability. For example, U.S. Pat. No. 6,420,182 discloses a method for fetal gender detection by assaying the pH of maternal urine after the 12th to 14th week of pregnancy. The test is based on the hypothesis that women bearing female fetuses have acidic urine, but the accuracy of this method is only about 65%. In another assay, a colorimetric test on urine from pregnant women may be performed after the 20th week of pregnancy. U.S. Pat. No. 4,840,914. The accuracy of this test in determining fetal gender was similarly low, only about 60%.
The applicant has noted that an evaluation of the reducing/oxidizing activity of a urine sample from a pregnant female provides a better method in determining fetal gender. Depending upon the processing and assay methods, the hormones which can contribute to the reducing activity of a urine sample are progesterone, testosterone and human chorionic gonadotropin (hCG), whereas estrogens can contribute to the oxidizing activity of the urine. The primary hormones directly linked to fetal gender are sex hormones, namely, testosterone and estrogens. The overall reducing/oxidizing activity of the urine sample from a pregnant mother carrying a male fetus is different from the overall reducing/oxidizing activity of the urine sample from a pregnant mother carrying a female fetus allowing for determination of fetal gender.
There is a continuing need to develop a simple, non-invasive and reliable method for determining the gender of an unborn child as early as possible after conception. There is also a need for pre-conception baby gender planning using a simple, non-invasive and reliable technique. Because human and other mammals have similar reproductive biology, these methods may also be of great commercial value to animal breeders.